dt-bindings: vendor-prefixes: add T-Head Semiconductor

Add vendor prefix for T-Head Semiconductor [1] [2]

[1] https://github.com/T-head-Semi
[2] https://www.t-head.cn/



Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: devicetree <devicetree@vger.kernel.org>
Link: https://lore.kernel.org/r/20211103020921.3870764-1-guoren@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>